1. Field of the Invention
The present invention relates to an apparatus for supplying treatment gas which provides for positioning of discharge nozzles close to workpieces during apparatus operation while resisting damage to such workpieces. It also provides a cooling, heating, wiping or drying system for various workpieces including coils of material such as metal coils and, more specifically, it relates to such a system which is adapted for high speed, thermally efficient processing of metal strip.
2. Description of the Prior Art
It has long been known that for many purposes a combination of materials may provide an advantageous blend of properties for a given product. Among such combinations are the coating of steel strip with a relatively thin layer of zinc in a galvanizing process.
In respect of continuous galvanizing, a steel coil provides a continuous strip which is immersed in a molten bath of zinc, is passed through a furnace and is subsequently cooled prior to recoiling. Various types of cooling means for such systems have been known. See, generally, Metal Producing, July, 1990, pages 33, 53.
It has been known in the galvanizing art to employ elongated rigid cooling tubes having longitudinal slots therein. Such tubes are positioned relatively close to the strip being cooled, e.g., on the order of about 5 inches. A number of problems have arisen from such constructions. More specifically, the close proximity of the slots to the strip has resulted in inefficient air flow as the spent gas which has already had contact with the strip surface tends to be re-entrained or interfere with efficient flow of the cooling gas from the slots to the strip surface. Also, occasionally either the strip or the slotted tube would be damaged as a result of undesired contact therebetween.
A general disclosure of the use of plates with orifices or jet tubes in heating, cooling, or drying of various industrial products is contained in Jet Impingement Heat Transfer From Jet Tubes in Orifices, National Heat Transfer Conference, 1989, HTD-Vol. 107, pages 43-50. While not specifically directed toward the cooling of metal strip, the concept of multiple jets for impinging air on a plate and exhausting such air is discussed.
My prior U.S. Pat. No. 5,201,132 discloses a system and an associated method for cooling, heating, wiping or drying strip, such as metal strip. It provides the use of a single unit or a pair of units having a source of gas, a plenum, and a plurality of fixed nozzles which are adapted to direct gas onto a passing strip.
There has been a significant problem in respect of the need to treat coils of materials, such as metal coils, particularly with respect to cooling the same. For metal or steel coils that have been heated during processing, such as in hot rolling, it is not uncommon, particularly during summer months in a warm climate for it to take a coil several days to cool to ambient temperatures. Obviously, an effective means for accelerating cooling of coils could expedite transport of the coil to either further working within the same plant, or shipment to a customer.
There has also been a problem with respect to prior art systems having rigid nozzles, in some instances, coming into undesired contact with the workpiece and risking damage to both, or restricting access and visibility of portions of the system to plant workers.
There remains, therefore, a very real and substantial need for improved cooling, heating, wiping and drying systems for elongated coils of material, such as metal coils. There is a further need for a system which would involve delivery of gas for treatment of any desired type while minimizing the risk of damage to equipment or workpieces by contact between the workpiece and the coils, as well as for means for permitting increased access of floor workers and maintenance people to the system.